feat(bal): Group A (timestamps + statuses + anticipate docs) and Group B (auto-sign) v0.3.4

Bump plugin version to 0.3.4 (manifest, __init__, plugin_base, VERSION).

GROUP A
- A1: remove block-height locktimes; the plugin now uses UNIX timestamps
  only. The NLOCKTIME_BLOCKHEIGHT_MAX guard is kept on purpose (it forces
  every locktime to be a timestamp). chk_locktime is now 2-arg; int_locktime
  and anticipate_locktime no longer accept blocks; RAW input only accepts d/y.
  Two now-dormant configs (LOCKTIME_BLOCKS, LOCKTIMEDELTA_BLOCKS) are kept with
  comments to avoid touching persisted keys.
- A2: rename PENDING -> MEMPOOL everywhere (label 'Mempool', yellow #ffce30);
  add new UPDATED status; ANTICIPATED & UPDATED keep VALID; documented
  set_status rules; backward-compat migration (old PENDING -> MEMPOOL).
- A3: clarify that anticipating to a future date only rebuilds (never
  invalidates), while only a past locktime invalidates (WillExpired). Code was
  already correct; only the comment and docs were fixed.

Colour follow-up: UPDATED lightened from #800080 to #b266b2 (more readable),
updated in theme.py, docs and the theme test.

GROUP B
- B1: verified the 'Create your will' button already opens the guided wizard
  (no code change needed).
- B2: new persisted AUTO_SIGN setting (default ON) with an 'Auto-sign on Check'
  checkbox in the settings dialog. When enabled, Check signs and broadcasts
  automatically; the wallet password is requested only for encrypted wallets.

B2 follow-up (fixes reported after testing):
- Remove the duplicate sign/broadcast cycle in lists.check(); build_will_task()
  already signs and broadcasts.
- Suppress the manual 'press Sign/Broadcast' hint and its popup when AUTO_SIGN
  is ON (kept when OFF).
- Make broadcast one-shot: removed the retry flag and the Exception('retry');
  failed will-executors stay PUSH_FAIL and are skipped (no endless retry).
  PUSHED transactions are already excluded from re-collection.

Docs: inheritance-options.md/.html and inheritance-flow.svg updated to v0.3.4.
Tests: 206 passing (new test_anticipate_manual_locktime, test_anticipate_past_locktime,
test_group_b_auto_sign; updated core/util, core/will_extra, gui/theme, gui/widgets).
CHANGELOG.md added with one numbered entry per task.

docs/images/inheritance-flow.svg

@@ -23,7 +23,7 @@
 
   <!-- Title -->
   <text x="24" y="34" font-size="20" font-weight="700">BAL — Inheritance change decision flow</text>
-  <text x="24" y="56" class="sub">What happens to your pre-signed transactions when you change the will (v0.3.3)</text>
+  <text x="24" y="56" class="sub">What happens to your pre-signed transactions when you change the will (v0.3.4)</text>
 
   <!-- Legend -->
   <g transform="translate(760,76)">
@@ -63,32 +63,32 @@
   <path class="edge" d="M420,256 L300,256"/>
   <text x="330" y="250" class="lbl">No</text>
 
-  <!-- D earlier? -->
+  <!-- D new date in the past? -->
   <polygon class="dec" points="590,312 800,350 590,388 380,350"/>
-  <text x="590" y="346" text-anchor="middle">VALID tx with locktime</text>
-  <text x="590" y="362" text-anchor="middle" class="sub">earlier than the new date? (anticipate)</text>
+  <text x="590" y="346" text-anchor="middle">New delivery date</text>
+  <text x="590" y="362" text-anchor="middle" class="sub">already in the PAST?</text>
   <path class="edge" d="M590,290 L590,312"/>
 
-  <!-- D Yes -> E -->
+  <!-- D No -> AN anticipate? -->
   <polygon class="dec" points="930,312 1110,350 930,388 750,350"/>
-  <text x="930" y="346" text-anchor="middle">Already signed</text>
-  <text x="930" y="362" text-anchor="middle" class="sub">or sent?</text>
+  <text x="930" y="346" text-anchor="middle">Moved the date</text>
+  <text x="930" y="362" text-anchor="middle" class="sub">EARLIER? (anticipate)</text>
   <path class="edge" d="M800,350 L750,350"/>
-  <text x="772" y="344" class="lbl">Yes (earlier)</text>
+  <text x="772" y="344" class="lbl">No (still future)</text>
 
-  <!-- E No -> R1 rebuild -->
+  <!-- AN Yes -> R1 rebuild (never invalidates) -->
   <rect class="rebuild" x="820" y="410" width="220" height="48" rx="8"/>
-  <text x="930" y="430" text-anchor="middle" class="ttl">Rebuild only</text>
-  <text x="930" y="446" text-anchor="middle" class="sub">no on-chain cost</text>
+  <text x="930" y="428" text-anchor="middle" class="ttl">Rebuild only</text>
+  <text x="930" y="444" text-anchor="middle" class="sub">no on-chain cost - NEVER invalidates</text>
   <path class="edge" d="M930,388 L930,410"/>
-  <text x="940" y="402" class="lbl">Not signed</text>
+  <text x="940" y="402" class="lbl">Yes (signed or not)</text>
 
-  <!-- E Yes -> INV2 -->
+  <!-- D Yes (past) -> INV2 -->
   <rect class="inval" x="820" y="476" width="240" height="48" rx="8"/>
   <text x="940" y="496" text-anchor="middle" class="ttl">Invalidate on-chain FIRST</text>
-  <text x="940" y="512" text-anchor="middle" class="sub">WillExpired</text>
-  <path class="edge" d="M1010,386 C1090,430 1080,460 1010,476"/>
-  <text x="1058" y="430" class="lbl">Signed</text>
+  <text x="940" y="512" text-anchor="middle" class="sub">WillExpired (date in the past)</text>
+  <path class="edge" d="M800,350 C1010,355 980,440 980,476"/>
+  <text x="806" y="372" class="lbl">Yes (past)</text>
 
   <!-- D No -> F -->
   <polygon class="dec" points="430,420 620,458 430,496 240,458"/>